code: def forward(self, inputs, mask=None):
      hidden = inputs
      for layer in self.layers:
          hidden = layer(hidden, mask=mask)
      return hidden
  
imports: import logging
  import torch
  from torch import nn
  from torch.nn import functional
  from ludwig.utils.torch_utils import get_activation, LudwigModule
label_desc: Use image node_id 3 for calling the TransformerStack obj's underlying member method code with example usage: obj.forward(inputs, mask) and returns: hidden